The perception of automotive quality is a key component in the marketing of motor vehicles, particularly passenger cars, in the North American market. The consumer will often consider cosmetic attributes as much as other attributes in developing this perception of automotive quality. How well the trim parts fit, how well the doors close, how smooth the line of the car, contribute as much to the perception of quality of the vehicle as the evaluation of the more significant operational components such as the power train and suspension. The impact of these issues on the perception of quality, and, in turn, their impact on automotive sales, provide a stimulus to automobile manufacturers to focus on improving the fit of the final trim parts on the exterior of motor vehicles.
Automobile manufacturing is a high volume industry. Premium is placed on the speed of manufacturing. Power tools, both electric and pneumatic, have been highly integrated into the production processes. To facilitate the use of power tools, a variety of technologies have been developed. Such things as guide screws and grommets have been incorporated to facilitate the rapid placement of parts that have to be aligned with precision.
However, these devices cannot be used with finished surfaces. Guide screws can mar the finish of the finished surface, and flexible grommets which are customarily used to take up build variation do not meet customer expectations for finished surfaces. The customer expects the vehicle lines and surfaces to be unobstructed and unmarred. The processes involved in the alignment of trim parts must be designed with both the precision of the alignment and the final appearance taken into account.
Epoxides (also known as expoxies or epoxy agents) have been considered as a substitute for grommets and gaskets in manufacturing processes. The most common types of agents used in epoxides are known as binary agents. Binary agents involve two components which are chemically inert when separated, but when they come into contact with each other (i.e., mix) they react to form a strong chemical bond therebetween. The chemical reactions involved may be exothermic which means they produce heat, or endothermic which means they require heat or some other form of energy to proceed to completion.
In a typical manufacturing application involving the bonding together of two parts, either one part would be treated with the first component of the binary agent and the mated part would be treated with the other component, or a pre-mixed epoxide would be placed onto one or both of the parts immediately upon the mixing. When the parts are joined, the binary agents may react exothermically or endothermically to proceed to completion. This process is known in the art as curing. Once the epoxide has cured, a strong bond is formed between the two epoxy materials. This technology has been developed to serve as a fastener material in a wide variety of applications.
One difficulty with thermal curing is that precisely mated surfaces, with very tight tolerances, may be distorted by the amount of heat involved in the epoxification process. In particular, the tolerances required for trim part alignment are much too tight to be used in conjunction with thermal curing. Another difficulty with thermal curing is that there is a minimum duration required during which the parts being bonded need to be held in place until the epoxides are sufficiently stiff such that the parts are rigidly affixed to each other.
To provide rapid set (hardening) and avoid spot heating of the epoxide at the point of reaction, a known technique is to apply an epoxide fixing accelerant to the surface of the epoxide.
One epoxide fixing accelerant technology that has developed over the years is ultraviolet (U-V) epoxide surface fixing. In this process, the epoxy agents used in the expoxification reaction are exposed to U-V light, as for example via U-V diodes, as a source of energy. The epoxide surfaces are tacked together strongly by fusing the surface molecules of the two agents, thereby creating a strong surface bond. This provides a rapid stiffness in which two surfaces become mutually affixed, while the chemical curing process can be allowed to proceed at a slower speed where during the reaction may operate at lower temperatures, not requiring external heating, which, in turn, eliminates thermal distortion of the surfaces. A common application of this technology is in the dental arts.
Another epoxide fixing accelerant technology that has also been developed is the use of a liquid epoxide accelerator (also known as a liquid epoxide curing agent or a liquid epoxide activator), to promote curing through chemical means, by lowering the energy required to complete the chemical reactions involved in the epoxide curing (fixing), thereby speeding up the curing process. Typically, the liquid epoxide accelerator is deployed as a spray (aerosol) upon the epoxide.
Accordingly, what remains needed in the art is a means to align finished trim parts with respect to a primary finished surface, and simultaneously bond the trim part to a secondary structural surface without the marring of finished surfaces.